Lithography technology that plays a key role in advancement of miniaturization of semiconductor devices is used to perform a significantly important process, in which a pattern is uniquely generated, among semiconductor manufacturing processes. In recent years, a design rule required for the semiconductor devices becomes finer year by year in accordance with high integration of LSI. In order to form a desirable circuit pattern for these semiconductor devices, a highly accurate original pattern (also referred to as a reticle or a mask) is needed. The highly accurate original pattern is produced using electron beam pattern writing technology in which high resolution is achieved.
An electron-beam pattern writing apparatus forms a shot having a size and a shape which are prepared depending on a figure pattern. Specifically, after an electron beam emitted from an electron gun assembly is shaped through a first shaping aperture plate into a rectangle, a deflector deflects the electron beam on a second shaping aperture plate. The beam shape and size is a target shape and size. Then, the electron beam is used in irradiating a sample disposed on a stage (for example, see Japanese Patent Application Publication No. 2007-43078 and Japanese Patent Application Publication No. 2013-45876). The electron beam passes through the first shaping aperture plate and the second shaping aperture plate so as to be formed into an electron beam having a certain shape and size.
Japanese Patent Application Publication No. 2013-45876 discloses an electron-beam pattern writing apparatus in which deflectors are disposed in two stages such that a shape of an electron beam is determined through deflection by the first deflector and a size of the electron beam is determined through deflection by the second deflector. In this electron-beam pattern writing apparatus, the first deflector produces a large deflection amount and operates at a low speed, while the second deflector produces a small deflection amount and operates at a high speed. Therefore, the order of shots is arranged according to beam shapes and settling time required for a digital-analog conversion (DAC) unit of the deflector is shortened. Accordingly, a pattern writing throughput is increased.
High current density is effective to shorten pattern writing time (shot time) of each shot. However, when a current is increased, inter-electron Coulomb interaction (Coulomb effect) causes beam resolution to deteriorate (blur) and a fine pattern cannot be formed. Therefore, the first shaping aperture plate size is limited and the maximum shot size is limited such that the current does not exceed a certain value.
In the electron-beam pattern writing apparatus, the maximum shot size becomes smaller in accordance with miniaturization of a pattern to be written. When a pattern for which high accuracy is not needed, such as a pattern for a peripheral circuit section, is written in a small shot size, the number of shots in total increases and time for writing the entire pattern increases.
Japanese Patent Application Publication No. 2007-43078 discloses that the first shaping aperture plate size is increased and pattern writing is performed for a pattern for which high accuracy is not needed, using a large shot size so as to shorten pattern writing time, and pattern writing is performed for a pattern for which high accuracy is needed, using a small shot size. Although it is considered that such a method is applied to the electron-beam pattern writing apparatus disclosed in Japanese Patent Application Publication No. 2013-45876, in the electron-beam pattern writing apparatus in which the deflectors are configured to form two stages so as to increase the pattern writing throughput, the second deflector that determines the size of the electron beam is designed to produce a small deflection amount. Therefore, a size of the maximum shot size determined by the size of the first shaping aperture plate is limited to a range of the shot size that can be changed through deflection by the second deflector and it is not possible for the maximum shot size to be greater than the range.
As above, in the related art, taking into account the deterioration of the beam resolution by the Coulomb effect and the deflection amount by the second deflector, the first shaping aperture plate size is limited and the maximum shot size becomes smaller. Therefore, problems arise in that the number of shots increases, pattern writing time for pattern writing of an entire pattern is increased, and the pattern writing throughput is decreased.